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From Norman Tuttle <ntut...@opendemand.com>
Subject Two questions regarding APR system calls (and their interaction with the operating system)
Date Tue, 21 Oct 2003 16:26:45 GMT
1) apr_time_now(): We have some concern about the accuracy of the 
timings, especially on a Windows platform. Unix is using the 
gettimeofday() system call, which is pretty standard, then outputs the 
calculated value of microseconds based on the returned structure. 
Windows (win32) uses a GetSystemTime() call, and then two other calls to 
convert that ultimately to an acceptable form in microseconds (I 
understand that the granularity available to Windows is really limited 
to milliseconds). I was interested in knowing whether using any of these 
intermediate functions limits the accuracy, what is the real timing 
granularity available from these operating systems (or the limitations 
of trying to read time in this manner), and how the operating systems 
manage to maintain the system time while juggling other threads and 
processes which request it in real time.

2) When attempting to use a load testing tool we have been developing 
with the help of the Apache library, to similate 200 users which are 
being generated over a cable modem connection, the apr_socket_connect() 
function returns a non-zero value, which from a Windows system 
represents its WSAETIMEDOUT error code. Current Apache Flood also 
displays the same error, and I get similar socket connection failures 
when running my same system using the Linux operating system  (Red Hat 
7.3) after I recompiled the same software to run from it. I am guessing 
that the error is probably a result of not having enough bandwidth 
through my cable modem connection to sustain 200 simultaneous 
connections (to get responses quickly enough); (a) does this sound 
(b) Is there any way to tweak "connect()" so that it allows more time 
for the socket to connect, or is trying to simulate 200 users just 
asking for too much in that arena (when communicating over cable modem)?

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